The technique of in-mould labelling (IML) has been known for many years. It involves the use of paper or plastics labels which ultimately form an integral part of the moulded product. The in-mould labels must, therefore, be able to tolerate the heat applied during the moulding process. The resultant product is a pre-decorated item, such as a container or the like, which may be filled thereafter. In contrast to glue applied or pressure-sensitive labels which appear above the surface of the container, in-mould labels appear as part of the container. Effectively, in-mould labelling eliminates the need for a separate labelling process following the manufacture of the container, which reduces labour and equipment costs.
In-mould labels generally comprise a carrier base, consisting of a polymeric or cellulosic carrier film, on which a decorative pattern or a written message is printed. The thus obtained label is subsequently positioned against a wall of a mould for injection moulding or for blow moulding or the like, held in place by various means, such as electrostatic forces or vacuum suction, and a polymeric article is moulded by injecting a mass of polymeric melt or by blowing a polymeric parison against the mould walls on which the in-mould label is applied. The adhesion of such labels to the polymeric article can be enhanced by applying a heat sealable layer (a film or a coating) onto the backing side (i.e., not printed surface) of the in-mould label which is to be in contact with the polymeric article.
In-mould labels can be used to cover a portion of a container or to cover the entire outer surface of a container. In the latter case, the in-mould label serves as an additional layer and may, therefore, enhance the structural integrity of the container.
Laminate films or multi-layer films are also well known and have particular packaging applications in the food industry, and pharmaceutical, medical and health care products. An important aspect of laminate films when used in packaging food, for example, is to prevent the ingress of moisture and air into the container which would otherwise cause the food therein to degrade undesirably quickly.
To counteract this effect, US 2009/0061062 describes a multilayer film having an active oxygen barrier and at least one layer containing an iron-based scavenging composition. In particular, ethylene vinyl alcohol copolymer (EVOH) is known as a good oxygen barrier material, and is widely used in conjunction with multi-layer packaging films. Oxygen barrier materials are employed in retort processes such as retort sterilisation and retort cooking. In retort processes, heat and pressure are used to cook or sterilise food in a sealed package. Retort conditions can be demanding with temperatures typically ranging from 115° C. to 130° C. under pressurised steam. However, under these retort conditions, many oxygen barrier polymers including EVOH can become damaged, distorted, delaminated, or they may lose their oxygen barrier properties during or after retorting due to absorbed moisture. The Oxygen barrier properties of the EVOH layer of a multi-layer film are reduced if exposed to high humidity. Therefore, the EVOH layer is usually protected by an outer layer that has good moisture barrier properties (such as polypropylene). However under the high temperature conditions experienced during the retort process, the moisture barrier properties of the protective layer is dramatically reduced. This phenomenon is known as “retort shock” in which moisture is trapped in the oxygen barrier layer, such as EVOH, during the retort process—thus leading to a drop in the barrier properties of the EVOH layer so as to allow the ingress of oxygen into the container.
There is a need for an article, such as food packaging or the like, involving in-mould labelling which does not suffer from the above-mentioned disadvantages. From the description that is to follow, it will become apparent how the present invention addresses the above-mentioned deficiencies associated with prior art constructions, while presenting numerous additional advantages not hitherto contemplated or possible with prior art techniques.